Clara Cell 10 kDa Protein Alleviates Murine Hepatitis Virus Strain 3-Induced Fulminant Hepatitis by Inhibiting Fibrinogen-Like Protein 2 Expression

Yu, Haijing; Liu, Yang; Wang, Hongwu; Wan, Xiaoyang; Huang, Jiaquan; Yan, Weiming; Xi, Dong; Luo, Xiaoping; Shen, Guanxin; Ning, Qin

In the current study, we used co-immunoprecipitation to analyze binding between CC10 and Fgl2. In this study, we investigated possible protein-protein interactions between CC10 and Fgl2 in vitro. The Chinese hamster ovary (CHO) cells transfected with pcDNA3.1-hCC10 and pcDNA3.1-hFgl2. Cellular proteins were immunoprecipitated with anti-CC10 antibody or anti-Fgl2 antibody. Immunoblotting was performed with anti-Fgl2 and anti-CC10 antibodies. Immunoprecipitation of protein extracts from pcDNA 3.1-CC10 and pcDNA3.1-Fgl2 co-transfected CHO cells with anti-Fgl2 or anti-CC10 antibody followed by western blotting with Fgl2 and CC10 antibodies indicated that CC10 did not co-immunoprecipitate with Fgl2, showing that there is no direct relationship between CC10 and Fgl2 (data not shown). The results showed that CC10 has no direct interaction with Fgl2. From our previous study the gene of fgl2 contributed profoundly in MHV-3 induced fulminant hepatitis and is extensively expressed in macrophages and endothelium (12, 33) . Our microarray indicated a CC10 down-regulated fgl2 expression and this is further confirmed by qPCR and Western blotting in vivo (peritoneal macrophages) and in vitro (THP-1, macrophage cell line). Therefore, it is reasonable to focus on macrophages to display the effect of CC10 on fgl2 expression and eventually mice survival. We entirely agree there may be other possibilities for a protective effect of CC10 to contribute to the disease process. This is worth further studies. The potential receptor of CC10 has not been revealed yet. Our previous study have demonstrated that CC10 have effect of dendritic cells in allergic rhinitis (34) . In this research, we evaluated the effect of CC10 on macrophages functions and found Fgl2 was substantially down-regulated upon CC10 treatment, therefore, we speculate that potential CC10 receptor may be also expressed on macrophages. The potential target of CC10 on other immune cells cannot be excluded.